Tissue ablation probes and methods for treating osteoid osteomas

ABSTRACT

A method of treating bone tissue (e.g., a tumor, such as an osteoid osteoma) is provided. The method comprises introducing an ablation probe into bone tissue, deploying at least one ablative element transversely from the probe into the bone tissue, and convoying ablation energy from the ablative element(s) to ablate the bone tissue. In one method, the ablative element(s) comprises a pair of ablative elements, in which case, the ablative elements are transversely deployed from the ablation probe in opposite directions. In another method, the ablative element(s) comprises a plurality of ablative elements, in which case, the ablative elements are transversely deployed outward from the ablation probe in a plane. The ablation energy conveyed from the ablative element(s) may have a non-spherical profile, e.g., an elongated profile, to match a non-spherical profile of the bone tissue to be treated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119 to U.S.Provisional Application Ser. No. 60/755,663, filed on Dec. 29, 2005which is incorporated herein by reference.

FIELD OF INVENTION

The present invention relates generally to tissue ablation devices and,more specifically, to tissue ablation probes for ablating tissue, suchas cancerous bone tissue.

BACKGROUND

Osteoid osteomas are benign, but painful, tumors that mainly occur inchildren and young adolescents, accounting for 10-12 percent of benignbone tumors with 80 percent of patients being between 5-24 years of age.Most osteoid osteomas are elongated in shape, have little or no growthpotential, and rarely exceed 1.5 centimeters in diameter. There aretypically three approaches to treatment: (1) medical treatment, whichincludes the administration of aspirin or other nonsteroidalanti-inflammatory agents that can be used in the long term; (2) surgicaltreatment, which involves resecting the tumor from the bone: and (3)radio frequency (RF) treatment, which involves percutaneously insertingan ablation needle within the bone and ablating the tumor with RFenergy.

With regard to medical treatment, the pain is often intolerable andlong-term use of nonsteroidal anti-inflammatory agents can result ingastrointestinal side effects. Surgery can be challenging due todifficulties in identification, incomplete removal of the tumor, and theadverse effect of the resection on a weight-bearing bone. RF ablationhas become the method preferred by most doctors, because of itspercutaneous, less invasive advantages. This technology allows the tumorto be ablated (burnt) by an electrode that is placed in the center ofthe nidus of the tumor.

Currently, percutaneous RF ablation can be accomplished using a multipleneedle electrode probe or a single needle electrode probe. Multipleneedle electrode probes are intended for soft tissue tumors and aresomewhat limited in bone tumor applications, mainly due to therelatively small size of osteoid osteomas and the difficulty ofpenetrating the hard bone tissue with the relatively flexibleelectrodes. Although the size and hard tissue penetration considerationsof single needle electrode probes are more ideal, the greatest challengewhen using single-needle probes is to create the largest ablation areato coincide with the elongated geometry of the tumor. However, becausesingle needle electrodes tend to favor a spherical ablation, theelongated osteoid osteomas mast be treated with multiple ablations,requiring the electrode to be repositioned for subsequent ablations inorder to prevent or minimize the destruction of healthy tissue.

There, thus, remain a need to provide tissue ablation probes and tissueablation methods for treating tumors within bone tissue, such as osteoidosteomas.

SUMMARY OF INVENTION

In accordance with one aspect of the present inventions, a method oftreating bone tissue (e.g., a tumor, such as an osteoid osteoma) isprovided. The method comprises introducing an ablation probe into bonetissue (e.g., percutaneously), deploying at least one ablative elementtransversely from the probe into the bone tissue, and conveying ablationenergy from the ablative element(s) to ablate the bone tissue. In onemethod, the ablative element(s) comprises a pair of ablative elements,in which case, the ablative elements are transversely deployed from theablation probe in opposite directions. In another method, the ablativeelement(s) comprises a plurality of ablative elements, in which case,the ablative elements are transversely deployed outward from theablation probe in a plane. The ablation energy conveyed from theablative element(s) may have a non-spherical profile, e.g., an elongatedprofile, to match a non-spherical profile of the bone tissue to betreated.

The ablative element(s) may have any configuration that allows them tobe transversely deployed from the ablation probe. For example, eachablative element may comprise a distal tip that can be deployed into thebone tissue by advancing the distal tip through the bone tissue. Or,each ablative element may be deployed into the bone tissue by bowing theablative element transversely outward from the ablation probe. In thelatter case, each ablative element may comprise a tissue cutting edgethat cuts through the bone tissue as the ablative element is radiallybowed outward from the ablation probe. In an optional method, theablative element(s) are deployed incrementally, and ablation energy isconveyed from the ablative element(s) between incremental deployments ofthe ablative element(s).

In accordance with another aspect of the present inventions, anothermethod of treating bone tissue (e.g., a tumor, such as an osteoidosteoma) is provided. The method comprises introducing a probe into bonetissue, e.g., percutaneously, deploying at least one electrodetransversely from the probe into the bone tissue, and conveying radiofrequency (RF) energy from the electrode element(s) into the bonetissue. The electrode element(s) may be arranged in the same manner asthe ablative element(s) discussed above. The RF energy conveyed from theelectrode element(s) has a therapeutic effect, e.g., by ablating thebone tissue.

Other and further embodiments and aspects of the invention will becomeapparent when reviewing the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and in the accompanying drawings, which may not bedrawn to scale, and in which:

FIG. 1 is a plan view of an ablation probe constructed in accordancewith one embodiment of the present inventions;

FIG. 2 is a plan view of an ablation probe constructed in accordancewith another embodiment of the present inventions;

FIG. 3 is a plan view of an ablation probe constructed in accordancewith still another embodiment of the present inventions, whereinablative elements are particularly shown in a retracted configuration;

FIG. 4 is a plan view of the ablation probe of FIG. 3, wherein theablative elements are particularly shown in a deployed configuration;

FIG. 5 is a cross-sectional view of the ablation probe of FIG. 3;

FIGS. 6A-6C are perspective views illustrating one method of operatingthe ablation probe of FIG. 1 to treat a bone tumor;

FIGS. 7A-7C are perspective views illustrating another method ofoperating the ablation probe of FIG. 1 to treat a bone tumor,

FIGS. 8A-8C are perspective views illustrating a method of operating theablation probe of FIG. 2 to treat a bone tumor; and

FIGS. 9A-9D are perspective views illustrating a method of operating theablation probe of FIG. 3 to treat a bone tumor.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1 illustrates a tissue ablation probe 100 constructed in accordancewith one embodiment of the present inventions. The tissue ablation probe100 comprises a delivery cannula 102 having a distal portion 104, andelectrodes 106 and 108 transversely deployable from a plurality ofopenings 114 in the side of the cannula 102. Optional coverings (notshown) may be provided over the openings 114. In one embodiment, theelectrodes 106 and 108 are mounted to an inner probe shaft (not shown)reciprocalably disposed within the cannula 102. Thus, distal movement ofthe inner probe shaft relative to the cannula 102 deploys the electrodes106 and 108 transversely outward from the cannula 102 collinearly inopposite directions, and proximal movement of the inner probe shaftrelative to the cannula 102 retracts the electrodes 106 and 108 withinthe cannula 102.

Deployment may be adjusted for various burn widths, depending upon thesize and dimensions of a target body. For example, if the osteoidosteoma to be treated is approximately 1 cm in width and 1 cm in length,the electrodes 106 and 108 may be deployed from the cannula 102 aminimal distance to create a matching circular ablation. If the osteoidosteoma to be treated is approximately 1 cm in width and 1.5 cm inlength, the electrodes 106 and 108 may be deployed from the cannula 102further to create a matching elliptical ablation. If the osteoid osteomato be treated is approximately 1 cm in width and 2.0 cm in length, theelectrodes 106 and 108 may be deployed from the cannula 102 even furtherto create a more elongated matching elliptical ablation.

In an optional embodiment, additional electrodes may be provided, suchthat the electrodes can extend transversely outward from the cannula 102in a plane. For example, a total of four electrodes may be provided,such that a 90 degree angle is formed between each adjacent pair ofelectrodes.

In the illustrated embodiment, the electrodes 106 and 108 are insulatedand have exposed electrode tips 110 and 112 to focus RF energy at thetips of the electrodes 106 and 108. Insulation may also ensure thatshort circuits do not occur when electrodes are fully retracted withincannula 102. When inserting the ablation probe 100 into the patient'sbody, the distal portion 104 of the cannula 102 may have a tip or otherpenetrating surface that aids insertion or placement into a tissue bodyor region (e.g., malignant or benign cancerous tissue such as an osteoidosteoma).

Once inserted (e.g., into the nidus of a tumor), the ablation probe 100may be coupled to a power source and RF energy may be supplied alongwires or filaments of electrodes 106 and 108. Once deployed, RF energymay be transmitted along electrodes 106 and/or 108 into target tissue.In some embodiments, a bipolar electrode configuration may beimplemented with ablation probe 100, with one of tips 110 or 112 actingas a supply (e.g., positive lead) and the other tip acting as a return.In other embodiments, a monopolar electrode configuration may beimplemented. In a monopolar configuration, tips 110 and 112 are positiveleads (i.e., “live”) and current flows from tips 110 and 112 to agrounding pad placed on the patient's body. By adjusting the deployedlength of electrodes 106 and 108 into a target region, an adjustableablation burn patient may be achieved to treat irregularly-shapedtumors, tissues, tones, and tissue bodies.

Thus, it can be appreciated that because the electrodes 106 and 108transversely extend outward from the cannula 102 in opposite directions,RF energy delivered to or between the electrodes 106 and 108 has anelongated profile. In the case where more electrodes are provided, someof the electrodes can be shorter than others to maintain the elongatedprofile of RF energy. For example, if four electrodes are utilized, oneopposing pair of the electrodes can be longer than the remainingopposing pair of electrodes.

FIG. 2 illustrates a tissue ablation probe 200 constructed in accordancewith another embodiment of the present inventions. The ablation probe200 includes an outer cannula having proximal portion 202 and distalportion 204. The ablation probe 200 also includes electrodes 206 and 208with respective electrode tips 210 and 212, and an inner cannula 214.Here, the inner cannula 214 may be configured to separate, slide, ormove proximal portion 202 and distal portion 204 away from each other toprovide an opening 216 out which the electrodes 206 and 208 may bedeployed.

When proximal portion 202 and distal portion 204 are moved together, theopening 216 closes. For example, electrodes 206 and 208 may retract intoinner cannula 214 and then proximal portion 202 and distal portion 204are moved together, closing the opening 216 and forming a seal betweenproximal portion 202 and distal portion 204. In some embodiments, a sealmay also include a gasket for creating a non-tight, air-tight,water-tight, or other type of seal between proximal portion 202 anddistal portion 204 when fully retracted. In other embodiments, when theopening 216 between proximal portion 202 and distal portion 204 isclosed, ablation probe 200 may be inserted or retracted into tissuewithin a target region. Like the ablation probe 100, the ablation probe200 may have a monopolar or bipolar electrode configuration, and mayhave more than two electrodes.

FIG. 3 illustrates a tissue ablation probe 300 constructed in accordancewith another embodiment of the present invention. The ablation probe 300includes a cannula having proximal portion 302 and distal portion 304,and a cage electrode array 306 that includes individual electrodes 308disposed between proximal portion 302 and distal portion 304. The endsof each individual electrode of cage electrode array 306 may be coupledor attached to proximal portion 302 and distal portion 304. In someembodiments, proximal portion 302 and distal portion 304 are coupledtogether by the cage electrode array 306. In other embodiments, proximalportion 302 and distal portion 304 may be coupled using anotherstructure, e.g., a mandrel 310 illustrated in FIG. 4. When pressure orforce is exerted (e.g., on a handle, proximal end of proximal portion302, mandrel, etc.), each of the individual electrodes of cage electrodearray 306 bows outward, creating a shaped deployment (e.g. anellipsoid), as illustrated in FIG. 4. By forcing the electrodesoutwards, the cage electrode array 306 may be deployed into surroundingtissue and RF energy supplied to ablate the desired tissue. The cageelectrode array 306 may be configured to form a pre-determined shape togenerate a desired ablation burn pattern. In an optional embodiment, ahandle (not shown) that holds the mandrel 310 can be configured to lockthe positions of the proximal and distal cannula portions 302, 304 inboth the retracted and deployed positions. This can be achieved withthreads or luer kicks.

The individual electrodes 308 of the array 306 may be alternatelyconfigured as live (i.e., supplying an electrical current, DC or AC) andground leads. As another embodiment, one side of the electrodes in cageelectrode array 306 may be live and the other half may be ground leads.In other embodiments, the mandrel 310 may have an area that, when cageelectrode array 306 is deployed, becomes exposed. The exposed area actsas a ground for the live electrodes of cage electrode array 306. Inother embodiments, only select electrodes 308 of the array 306 may beoperated to further shape the profile of the RF energy to the desiredshape. Thus, it can be appreciated that, like the ablation probe 100,the ablation probe 300 may have a monopolar or bipolar electrodeconfiguration.

By moving proximal portion 302 and distal portion 304 towards eachother, the individual electrodes 308 of cage electrode array 306transversely bow outward from the cannula and into the surroundingtissue, as illustrated in FIG. 4. By forcing the electrodes outwards,cage electrode array 306 may be deployed into surrounding tissue and RFenergy supplied to ablate the desired tissue. In some embodiments, theshape of each electrode of cage electrode array 306 may be configured toaid the deployment into different types of tissue (e.g., soft tissue,bone, and others). In one embodiment, the electrodes of the array 306may be shaped to enable each electrode to cut into tissue when theelectrode array is deployed, thereby aiding penetration of the array andimproving ablation effectiveness. For example, FIG. 5 illustrates theelectrodes 308 with triangular cross-sections, with one of the cornersof the triangles (i.e., the outer edge of the electrodes 308) formingthe cutting implement as the electrodes bow outward.

Having described the structure of the tissue ablation probes, their usein treating bone tissue, and specifically, a tumor (e.g., osteoidosteoma) within the cortical portion of a bone.

Referring now to FIGS. 6A-6C, the operation of the ablation probe 100 intreating an elliptically shaped tumor will not be described. First, theablation probe 100 is percutaneously introduced into the cortical regionof the bone in a conventional manner, such that the distal portion 104of the cannula 102 is centered within the tumor, (i.e., half of thetumor is disposed on one side of the cannula 102 and the other half ofthe tumor is disposed on the other side of the cannula 102) (FIG. 6A).In addition, the electrode openings 114 should be centered within thetumor (i.e., half of the tumor disposed above the electrode openings 114and the other half of the tumor disposed below the electrode openings114). Next, the electrodes 106 and 108 are transversely deployed outfrom the cannula 102 in opposite directions via the openings 114, suchthat the tips 110 and 112 of the respective electrodes 506 and 108advance through the tumor (FIG. 6B). As illustrated, the electrodes 106and 108 are advanced until the respective tips 110 and 112 are locatedat the periphery of the tumor. Next, RF energy is conveyed between theelectrodes 106 and 108 into the tumor in a bipolar configuration,thereby ablating the tumor (FIG. 6C). Alternatively, the RF energy maybe conveyed from the electrodes 106 and 108 in a monopolarconfiguration. As can be seen, the conveyed RF energy (shown by thearrows) has an elliptical profile that matches the elliptical shape ofthe tumor, thereby allowing the tumor to be efficiently treated withminimal damage to the surrounding healthy bone tissue. The electrodes106 and 108 can then be retracted within the cannula 102, and theablation probe 200 removed from the patient in a conventional manner.

In an optional method, the electrodes 106 and 108 may be incrementallydeployed, and RF energy can be conveyed from the electrodes 106 and 108between the deployments. Such a technique lends itself well to bonetumors that are too elongated to be treated with only one ablation. Forexample, referring to FIGS. 7A-7C, the electrodes 106 and 108 can bedeployed from the cannula 102 a first distance, and RF energy can beconveyed from the electrodes 106 and 108 to ablate the center of thetumor (FIG. 7A). The electrodes 106 and 108 can be advanced further fromthe cannula 102 a second greater distance, and RF energy can be conveyedfrom the electrodes 106 and 108 to extend the ablation outward from thecenter of the tumor (FIG. 7B). And then the electrodes 106 and 108 canbe advanced even further from the electrodes 106 and 108 to complete theablation of the bone tumor (FIG. 7C). As can be seen, the ablationenergy can be delivered in a monopolar arrangement. Alternatively, theablation energy is delivered in a bipolar arrangement.

Referring now to FIGS. 8A-8C, the operation of the ablation probe 200 intreating an elliptically shaped tumor will not be described. First, theablation probe 200, while the distal and proximal cannula portions 202and 204 are compressed together to seal the opening 216, ispercutaneously introduced into the cortical region of the bone in aconventional manner, such that the distal cannula portion 204 and theopening 216 are centered within the tumor (FIG. 8A). Next, distalcannula portion 204 is distally advanced relative to the proximalcannula portion 202, thereby exposing the opening 216 (FIG. 8B). Theelectrodes 206 and 208 are transversely deployed out from the opening216, such that the tips 210 and 212 of the respective electrodes 206 and208 advance through the tumor (FIG. 8C), and RF energy is conveyed fromthe electrodes 206 and 208 into the tumor, thereby ablating the tumor inthe same manner illustrated in FIG. 6C. The electrodes 206 and 208 canthen be retracted within the cannula, the distal cannula portion 204 canbe proximally advanced relative to the proximal cannula portion 202 toseal the opening 216, and the ablation probe 200 removed from thepatient.

Referring now to FIGS. 9A-9C, the operation of the ablation probe 300 intreating a disk-shaped tumor will not be described. First, the ablationprobe 300 is percutaneously introduced into the cortical region of thebone in a conventional manner, such that the distal cannula portion 304is centered within the tumor (FIG. 9A). Next, the electrodes 308 of thearray 306 are transversely deployed out from the cannula in a plane thatcoincides with the major plane of the flattened tumor by displacing thedistal cannula portion 306 relative to the proximal cannula portion 304to bow the electrodes 308 outward into the tissue (FIG. 9B). Next, RFenergy is conveyed from the electrode array 306 into the tumor in abipolar configuration, thereby ablating the tumor (FIG. 9C).Alternatively, the RF energy may be conveyed from the electrodes 308 ina monopolar configuration. As can be seen, the conveyed RF energy has adisk-like profile that matches the disk shaped tumor, thereby allowingthe tumor to be efficiently treated with minimal damage to thesurrounding healthy bone tissue. Alternatively, the lengths of theelectrodes 308 may be adjusted to manipulate the RF energy profile tomatch the shape of the tumor (FIG. 9D). The distal cannula portion 304can then be displaced distally relatively to the proximal cannulaportion 302 to retract the electrodes 308, and the ablation probe 300removed from the patient in a conventional manner.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the implementation of theseand other embodiments of the invention are not limited to the detailsand examples provided above.

1-46. (canceled)
 47. A tissue ablation probe, comprising: a cannulacomprising a proximal portion and a distal portion; and a plurality ofablative elements; wherein the proximal and distal portion of thecannula are coupled to each other by plurality of ablative elements; andwherein distally advancing the cannula proximal portion relative to thecannula distal portion urges the plurality of ablative elements to bowradially outward from the cannula.
 48. The tissue ablation probe ofclaim 47, wherein the plurality of ablative elements comprise fourablative elements separated from one another by approximately 90degrees.
 49. The tissue ablation probe of claim 47, wherein theplurality of ablative elements comprise a cage electrode array.
 50. Thetissue ablation probe of claim 47, wherein the plurality of ablativeelements have an elliptical profile when bowed radially outward from thecannula.
 51. The tissue ablation probe of claim 47, wherein theplurality of ablative elements have a spherical profile when bowedradially outward from the cannula.
 52. The tissue ablation probe ofclaim 47, wherein the plurality of ablative elements have anon-spherical profile when bowed radially outward from the cannula. 53.The tissue ablation probe of claim 47, wherein the plurality of ablativeelements have an elongated profile when deployed radially outward. 54.The tissue ablation probe of claim 47, wherein incrementally advancingthe cannula proximal portion relative to the cannula distal portionurges the plurality of ablative elements to incrementally bow radiallyoutward from the cannula.
 55. The tissue ablation probe of claim 47,wherein a proximal end of each of the plurality of ablative elements iscoupled to the proximal portion of the cannula, and a distal end of eachof the plurality of ablative elements is coupled to the distal portionof the cannula, thereby constraining the plurality of ablative elements.56. The tissue ablation probe of claim 47, wherein the plurality ofelectrodes are coupled to a power source.
 57. A tissue ablation probe,comprising: a cannula comprising a proximal portion and a distal portionslidable relative to each other to deploy at least one ablative element,the at least one ablative element extending transversely from thecannula when deployed.
 58. The tissue ablation probe of claim 57,wherein the at least one ablative element is mounted on an inner probeshaft.
 59. The tissue ablation probe of claim 57, wherein the at leastone ablative element comprises a pair of ablative elements configured tobe transversely deployed from the cannula in opposite directions. 60.The tissue ablation probe of claim 57, further comprising a seal formedbetween the proximal portion and distal portions when said proximal anddistal portions are in contact with one another.
 61. The tissue ablationprobe of claim 57, wherein sliding the cannula proximal portion awayfrom the cannula distal portion exposes an opening between the cannulaproximal portion and the cannula distal portion.
 62. The tissue ablationprobe of claim 61, wherein the at least one ablative element comprises apair of ablative elements configured to be transversely deployed throughthe cannula opening in opposite directions.
 63. The tissue ablationprobe of claim 62, wherein the pair of ablative element areincrementally deployed.
 64. The tissue ablation probe of claim 57,wherein the at least one ablative element includes a plurality ofablative elements symmetrically arranged about a plane of the cannula.65. The tissue ablation probe of claim 64, wherein the plurality ofablative elements are transversely deployed in opposite directions. 66.The tissue ablation probe of claim 64, wherein the plurality of ablativeelements are incrementally deployed in opposite directions.